1. Field of the Invention
This invention broadly relates to appliances that are used in the course of orthodontic treatment. More particularly, the present invention relates to a self-ligating orthodontic appliance such as a bracket or molar appliance having a latch that releasably retains an archwire in an archwire slot of the appliance.
2. Description of the Related Art
Orthodontic therapy is a specialized type of treatment within the field of dentistry, and involves movement of malpositioned teeth to orthodontically correct locations. Orthodontic treatment typically enhances the aesthetic appearance of the teeth, particularly in instances when the patient's front teeth are malpositioned or crooked. Orthodontic treatment can also improve the patient's occlusion so that the teeth function better with each other during mastication.
Many types of orthodontic treatment programs involve the use of a set of tiny appliances and wires that are commonly known collectively as “braces”. During such treatment programs, small slotted appliances known as brackets are fixed to the patient's anterior, cuspid and bicuspid teeth, and an archwire is inserted into the slot of each bracket. The archwire forms a track to guide movement of the teeth to orthodontically correct locations. End sections of the archwires are typically captured in molar appliances that are fixed to the patient's molar teeth.
Recently, there has been increased interest in orthodontic appliances that have a latch for retaining the archwire in the archwire slot. Appliances of this type are widely known as self-ligating appliances and often obviate the need to use ligatures (such as wire ties or elastomeric O-rings) for retaining the archwire in the archwire slots. Improved self-ligating orthodontic appliances having a self-releasing latch are described in applicant's U.S. Pat. Nos. 6,302,688 and 6,582,226.
A recently introduced self-ligating appliance known as “SMARTCLIP” brand appliance from 3M Unitek Corporation has a latch that comprises two resilient clips, and each clip has a generally “C”-shaped configuration. The clips spread open to admit an archwire into an archwire slot of the appliance. Each clip is connected to a body of the appliance by a post that extends through the clip. Each post has a neck and an enlarged head for retaining the clip, and the neck and the head both have semicircular shapes with common points of origin when viewed in directions toward the sides of the appliance.